Cyclones? Don't blame climate change

Cyclones will affect more people as coastal populations boom, according to the latest scientific statement (Image: Reuters/Carlos Barria)

Climate change can't be blamed for any of the events that made the past tropical cyclone season the worst in recent times, a report by a group of international experts says.

"No single high impact tropical cyclone event of 2004 and 2005 can be directly attributed to global warming," it says in a report submitted to the World Meteorological Organization's (WMO) Commission for Atmospheric Sciences, which is meeting in South Africa .

Dr John McBride is a principal research scientist at Australia's Bureau of Meteorology and reports to the WMO on the effects of climate change on tropical weather.

He is also chair of the international WMO committee that produced the report.

McBride says the report came as an attempt to separate fact from fiction in relation to recent controversy about the role of climate change in producing tropical cyclones.

McBride says there's no doubt that the latest season was the most ferocious in recent times, with a series of vicious cyclones including Hurricane Katrina that devastated New Orleans.

"These last two years were probably the most severe ... since the satellite era began [about 40 years ago]," he says.

But he says evidence linking this to climate change is inconclusive or lacking.

The case against climate change

A current argument suggests that as climate change causes the seas to warm the oceans store more energy that can be harnessed by the wind to form tropical cyclones.

But this is too simplistic, McBride says.

"There are other conditions that are necessary to be able to tap that energy source, such as the structure of the wind systems," he says.

McBride says there's no proof that cyclones have become more common or will become more frequent in the future, or that they'll take place in more parts of the world.

"Worldwide, there's really no evidence for any change," he says.

He says the report also questions claims that tropical cyclones have become more intense over the past 50 years, saying data used in the past may be inaccurate or incomplete because of limitations with the technology of the day.

The rising damage toll

McBride says it's true that the cost of cyclones, in terms of life and property, appears to be rising.

But he says this is because more people are living on the coast, not because cyclones are becoming more severe.

"There's a public perception that we're getting disasters everywhere and part of this is due to the fact that there are so many people living in vulnerable areas," he says.

"Given no change in tropical cyclone behaviour at all you will still get an increase in insurance damage and the financial scale of damage because of increasing coastal infrastructure."

Sea levels

What is of concern, McBride says, is strong evidence that sea levels are rising.

In this way climate change may have an indirect effect on the potential for tropical cyclones to cause damage because of increasing storm surges from the sea.

This means that even if there is no change in tropical cyclones their potential to cause death and damage will increase if sea levels rise, he says.